IARC classifications

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IARC classifications

The International Agency for Research on Cancer (IARC) have devised a system of categories to evaluate the carcinogenicity of an agent to humans[1]. An agent is classified based on scientific evidence derived from human and experimental animal studies and from mechanistic and other relevant data[2]. The list of categories and their definition are shown in Table 1.

Evidence of carcinogenicity in humans is less than sufficient but there is sufficient evidence of carcinogenicity in experimental animals and strong evidence in exposed humans that the agent acts through a relevant mechanism of carcinogenicity

111

Group 2A

Probably carcinogenic to humans*

Limited evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in experimental animals OR

Inadequate evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in experimental animals and strong evidence that the carcinogenesis is mediated by a mechanism that also operates in humans OR

Limited evidence of carcinogenicity in humans, but belongs, based on mechanistic considerations, to a class of agents for which one or more members have been classified in Group 1 or Group 2A

66

Group 2B

Possibly carcinogenic to humans*

Limited evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals OR

Inadequate evidence of carcinogenicity in humans but sufficient evidence of carcinogenicity in experimental animals OR

Inadequate evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals, but with supporting evidence from mechanistic and other relevant data

285

Group 3

Not classifiable as to its carcinogenicity to humans

Evidence of carcinogenicity is inadequate in humans and inadequate or limited in experimental animals OR

Evidence of carcinogenicity is inadequate in humans but sufficient in experimental animals, but strong evidence that the mechanism of carcinogenicity in experimental animals does not operate in humans OR

Agents that do not fall into any other group

Agents in Group 3 are not determined to be non-carcinogenic or safe overall, but often means that further research is needed.

505

Group 4

Probably not carcinogenic to humans

Evidence suggesting lack of carcinogenicity in humans and in experimental animals OR

Inadequate evidence of carcinogenicity in humans but evidence suggesting lack of carcinogenicity in experimental animals, consistently and strongly supported by a broad range of mechanistic and other relevant data

1

* The terms probably carcinogenic and possibly carcinogenic have no quantitative significance and are used simply as descriptors of different levels of evidence of human carcinogenicity, with probably carcinogenic signifying a higher level of evidence than possibly carcinogenic.